A plurality of combustors of a gas turbine are mounted annularly around a casing of the gas turbine. As shown in FIG. 3, a conventional combustor 51 has a pilot nozzle 52, and a plurality of main nozzles 53 arranged annularly around the pilot nozzle 52. In the case of a dual mode in which fuel is switched between oil fuel and gas fuel, the main nozzle 53 is of a structure having a path for passage of oil fuel and a path for passage of gas fuel. The pilot nozzle 52 also has a similar structure.    Patent Document 1: U.S. Pat. No. 4,258,544    Patent Document 2: Japanese Patent No. 3495730